The Black Cats have started the season poorly, winless in eight and devoid of any confidence.
However, they are not alone as rivals Newcastle United, Aston Villa and West Bromwich Albion have also struggled for form and look the most likely to be involved in a relegation scrap thus far.
The arrival of Sam Allardyce as Sunderland boss is a real boost for the Mackems, as announced on the club's official website, and Roberts feels their survival hopes could be pinned on how much Allardyce can get out of Defoe.
Indeed, speaking to Breathe Sport via his Twitter account, Roberts talks highly of the former West Ham United man and claims no other team among the bottom four has a striker equal to his level.
“Sunderland will have to make sure that Jermain Defoe is functioning at his highest level. I don’t believe there is anybody in the bottom four who has a striker of that level,” he claimed.
“He could be the difference between Sunderland staying up, and being relegated.”
Is Jermain Defoe the best striker in the bottom four?
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As per the table provided by Opta Stats, Defoe currently competes well with his Premier League rivals, but doesn’t particularly stand out in any of the key attacking categories.
Villa’s summer signing Rudy Gestede has netted the most goals of any striker in the bottom four so far this season, while also averaging the most shots on goal per Premier League encounter.
The Baggies duo of Saido Berahino and Salomon Rondon is a potentially excellent partnership, with the latter averaging the most key passes and touches per league match thus far.
Newcastle United’s Aleksandar Mitrovic has mostly hit the headlines for his poor disciplinary record, yet the Magpies man does have plenty of talent and will get better as the season goes on.
Defoe, now 33, can’t perform to the same standards as he used to, yet he does possess leadership qualities, footballing intelligence and awareness, which still gives him an edge.